Re: Leading Spaces and split()

On Fri, Aug 19, 2011 at 4:01 PM, Rothenmaier, Deane C. <
[email protected]> wrote:

>  Greetings, O Wise Ones…****
>
> ** **
>
> I’m trying to understand the behavior I’m getting from this code:****
>
> ** **
>
> #!Perl****
>
>
> ################################################################################
> ****
>
> # PROGRAM: array_test1.pl****
>
>
> ################################################################################
> ****
>
> ** **
>
> use strict;****
>
> use warnings;****
>
> ** **
>
> my $string1 = "Windows XP Professional Service Pack 2 (build 2600)
> Hewlett-Packard";****
>
> my $string2 = "            Windows XP Professional Service Pack 2 (build
> 2600) Hewlett-Packard ";****
>
> ** **
>
> my @ary1;****
>
> my @ary2;****
>
> ** **
>
> @ary1 = split( " ", $string1 );****
>
> ** **
>
> my ($win_type1, $win_ver1, $svc_pack1, $win_build1);****
>
> ** **
>
> $win_type1 = $ary1[1];****
>
> $win_ver1 = $ary1[2];****
>
> ** **
>
> for ($win_type1) {****
>
>    /XP/ && do {****
>
>       $svc_pack1 = $ary1[5];****
>
>       ($win_build1 = $ary1[7]) =~ s{\)}{};****
>
>       last;****
>
>    };****
>
> }****
>
> ** **
>
> print "Current Method...\n";****
>
> print "Type: \"$win_type1\", Version: \"$win_ver1\",\n";****
>
> print "Service Pack: \"$svc_pack1\", Build: \"$win_build1\"\n\n";****
>
> ** **
>
> my ($win_type2, $win_ver2, $svc_pack2, $win_build2);****
>
> ** **
>
> for ($string1) {****
>
>    /XP/ && do {****
>
>       ($win_type2, $win_ver2, $svc_pack2, $win_build2) = (split( /\s+/,
> $string1 ))[1, 2, 5, 7];****
>
>       last;****
>
>    };****
>
> }****
>
> ** **
>
> $win_build2 =~ s{\)}{};****
>
> ** **
>
> print "Proposed Method...\n";****
>
> print "Type: \"$win_type2\", Version: \"$win_ver2\",\n";****
>
> print "Service Pack: \"$svc_pack2\", Build: \"$win_build2\"\n";****
>
> ** **
>
> ** **
>
> ** **
>
> @ary1 = split( " ", $string1 );****
>
> ** **
>
> $win_type1 = $ary1[1];****
>
> $win_ver1 = $ary1[2];****
>
> ** **
>
> for ($win_type1) {****
>
>    /XP/ && do {****
>
>       $svc_pack1 = $ary1[5];****
>
>       ($win_build1 = $ary1[7]) =~ s{\)}{};****
>
>       last;****
>
>    };****
>
> }****
>
> ** **
>
> print "\nFILE string:\n";****
>
> print "Current Method...\n";****
>
> print "Type: \"$win_type1\", Version: \"$win_ver1\",\n";****
>
> print "Service Pack: \"$svc_pack1\", Build: \"$win_build1\"\n\n";****
>
> ** **
>
> for ($string2) {****
>
>    /XP/ && do {****
>
>       ($win_type2, $win_ver2, $svc_pack2, $win_build2) = (split( /\s+/,
> $string2 ))[1, 2, 5, 7];****
>
>       last;****
>
>    };****
>
> }****
>
> ** **
>
> $win_build2 =~ s{\)}{};****
>
> ** **
>
> print "Proposed Method...\n";****
>
> print "Type: \"$win_type2\", Version: \"$win_ver2\",\n";****
>
> print "Service Pack: \"$svc_pack2\", Build: \"$win_build2\"\n";****
>
> ** **
>
> ** **
>
>
> ################################################################################
> ****
>
> # PROGRAM OUTPUT: ****
>
>
> ################################################################################
> ****
>
> ** **
>
> Current Method...****
>
> Type: "XP", Version: "Professional",****
>
> Service Pack: "2", Build: "2600"****
>
> ** **
>
> Proposed Method...****
>
> Type: "XP", Version: "Professional",****
>
> Service Pack: "2", Build: "2600"****
>
> ** **
>
> FILE string:****
>
> Current Method...****
>
> Type: "XP", Version: "Professional",****
>
> Service Pack: "2", Build: "2600"****
>
> ** **
>
> Proposed Method...****
>
> Type: "Windows", Version: "XP",****
>
> Service Pack: "Pack", Build: "(build"****
>
> ** **
>
> The red text illustrates the error (if such it be?). My SWAG is that the
> “nothing” between Perl’s ‘^’ anchor and the first space in $string2 is
> what’s causing the problem. Can someone confirm this? Or provide me with the
> correct answer if I’m wrong?****
>
> ** **
>
> Thanks!****
>
> ** **
>
> Deane Rothenmaier****
>
> Programmer/Analyst – IT-StdCfg****
>
> Walgreens Corp.****
>
> 2 Overlook Point #N51022D****
>
> MS 6515****
>
> Lincolnshire, IL 60069****
>
> 224-542-5150****
>
> ** **
>
> I will make sure that my doomsday device is up to code and properly
> grounded. – Peter Anspach’s list of 100 things to do when one becomes an
> Evil Overlord****
>
>
>
Look at the documentation on the split function (perldoc -f split).
Particularly the section that states:
            As a special case, specifying a PATTERN of space (' ') will
            split on white space just as "split" with no arguments does.
            Thus, "split(' ')" can be used to emulate awk's default
            behavior, whereas "split(/ /)" will give you as many initial
            null fields (empty string) as there are leading spaces. A
            "split" on "/\s+/" is like a "split(' ')" except that any
            leading whitespace produces a null first field.

HTH, Ken

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